@color: blue;
@Color: green;
@witdh: 10px + 5px;

.my-mixin {
  color: black;
}

div {
  color: aliceblue;
  border: @witdh solid red;
  .my-mixin();
  div {
    color: @Color;
  }
  // &代表当前作用域
  &::after {
    content: '1';
  }
}